CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Operating revenue	$ 986,495	$ 1,040,462	$ 1,985,988	$ 2,192,727
Operating expenses:
Purchased transportation and warehousing	727,236	763,609	1,467,408	1,630,540
Salaries and benefits	141,856	141,823	286,352	279,254
Depreciation and amortization	37,772	35,386	76,103	70,835
Insurance and claims	12,639	11,676	25,257	24,359
General and administrative	27,877	26,757	55,111	52,298
Gain on sale of assets, net	(413)	(859)	(910)	(4,834)
Total operating expenses	946,967	978,392	1,909,321	2,052,452
Operating income	39,528	62,070	76,667	140,275
Other income (expense):
Interest expense	(3,689)	(3,116)	(7,588)	(6,086)
Interest income	1,808	2,087	3,201	3,463
Other, net	(66)	69	(236)	108
Total other expense, net	(1,947)	(960)	(4,623)	(2,515)
Income before provision for income taxes	37,581	61,110	72,044	137,760
Provision for income taxes	8,566	14,605	15,976	29,475
Net income	29,015	46,505	56,068	108,285
Other comprehensive income:
Foreign currency translation adjustments	(63)	44	(71)	78
Total comprehensive income	$ 28,952	$ 46,549	$ 55,998	$ 108,363
Basic earnings per common share	$ 0.48	$ 0.73	$ 0.92	$ 1.68
Diluted earnings per common share	$ 0.47	$ 0.72	$ 0.91	$ 1.66
Basic weighted average number of shares outstanding	60,710	64,074	61,018	64,586
Diluted weighted average number of shares outstanding	61,108	64,586	61,387	65,132